We've done DCL four times with little ones (age 1-7) and had a great time but our kids favourite cruise of all time was on the Norwegian Breakaway when they were 6 and 8. Great kids club, lots of activities for my daredevil daughter like bungy trampoline, rock climbing, ropes course, mini golf, etc. The shows weren't nearly as good or family friendly, but in everything else we'd say the cruise was as good or better than DCL. We're trying RCCL this fall as well. I agree that it's hard to beat Disney for the little ones, but as we get older we just feel that the value just isn't there anymore.
One note though, if you can only do the short cruises, I get the sense that DCL is heads and shoulders above the other lines that offer 3 and 4 day cruises. It seems that the "booze cruise" stereotype is alive and well on most other lines. Not that everyone behaves perfectly on Disney either! But for 7 day and more cruises, we've moved on from Disney and are finding great value on other lines.